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MITRAL STENOSIS
Joanne Cusack
BSE Breakdown
Recognition of rheumatic mitral stenosis Qualitative description of valve and sub-valve
calcification and fibrosis Measurement of orifice area by planimetry Factors favouring successful balloon valvuloplasty Doppler assessment of mean and end-diastolic
gradient Doppler assessment of area by ‘pressure half-
time‘: technique and limitations Role of exercise echocardiography in assessing
the change in transmitral gradient and pulmonary systolic pressures with exercise, as decision aid in the timing of surgery/balloon valvuloplasty
Use of Echo
Allows confirmation of diagnosis
Assessment of severity
Analysis of valve anatomy
Parasternal long axis
Parasternal short axis
Apical four chamber
Apical three chamber
Apical two chamber
Mitral Stenosis
Narrowing of the mitral valve
Restricts the flow of blood through the valve
Back pressure which builds up behind the narrowed valve can cause various problems and symptoms
The more severe the narrowing, the more serious the problems
Causes
Rheumatic Inflammation of the valve develops
(through exposure to streptococcus) which can cause permanent damage and lead to thickening and scarring years later
Congenital Hypoplasia of mitral valve, commissural
fusion, double orifice mitral valve, shortened or thickened chordae, parachute mitral valve
Degenerative severe annular calcification
Symptoms
Dyspnoea
Syncope
Angina
Chest infections
Haemoptysis
Assessment
Appearance of valve
Mitral valve orifice area
Severity of stenosis
Severity of mitral regurgitation
Suitability for balloon valvuloplasty
Appearance of stenotic valve
Thickening with restricted mobility, mainly of leaflet tips, leading to a characteristic diastolic doming of mobility pattern, especially of the anterior leaflet (known as the ‘hockey stick’)
Diastolic doming due to tethering of the leaflets by retracted and fused chordae tendinae and commissural fusion
Methods for Assessing the Mitral Valve Planimetry
Pressure half-time
Mean gradient
Measurement of mitral valve orifice area by planimetry Measurement should be taken in the
parasternal short axis view at the echocardiographic slice showing the smallest orifice area
Make sure section not oblique – the measurement plane should be perpendicular to the mitral orifice
Do not planimeter the chordae which, if thickened, can mimic the orifice
Use colour flow Doppler as a guide for the orifice if not obvious from 2-D image
Mitral Valve Area severity ranges
Normal 3 – 5 cm2
Mild > 1.5 cm2
Moderate 1 – 1.5cm2
Severe < 1cm2
Planimetry
Most accurate method for quantitating mitral stenosis – considered the reference measurement
Advantage - it is not influenced by accompanying mitral regurgitation or shunt defects.
Limitations - dropout of echoes from areas of calcification, the influence of gain settings and unreliability following balloon valvuloplasty.
Doppler assessment of area by pressure half-time method The time required for the mitral
diastolic pressure to fall by 50%
Mitral valve area is calculated as:
220 ⁄ pressure half time (msec)
Limitations of pressure half-time method Influenced by left ventricular filling
The presence of mitral regurgitation, aortic regurgitation and atrial septal defects may alter the validity of this technique
Doppler assessment of mean gradient Calculated as an average gradient
across the mitral valve
Measured by tracing around diastolic inflow Doppler signal
More reliable and reproducible by using continuous wave and increasing the sweep speed during measurement of the gradient
Severity of Mitral Stenosis
Mild Moderate Severe
Planimetred orifice area (cm2)
> 1.5 1.0 – 1.5 < 1.0
Pressure half-time (msec)
< 150 150 - 200 > 200
Mean gradient (mmHg)
< 5 5 - 10 > 10
PA systolic pressure (mmHg)
25 25 - 35 > 35
PA Systolic Pressure
Calculated using short form Bernoulli equation:
∆ P = 4 V 2 + RA pressure
(Where V is peak velocity of TR jet)
Estimation of RAp through IVC
Diameter on expiration (cm)
Collapse on inspiration (%)
Pressure estimate (mmHg)
< 2 complete 0 – 5
< 2 > 50 5 – 10
> 2 25 – 50 10 – 15
> 2 < 25 15 – 20
Right heart
Mitral stenosis obstructs blood flow into the LV
Left atrial pressure increases in proportion to the severity of the stenosis
This, in turn, restricts pulmonary venous return to the left atrium, elevating pulmonary vascular and, consequently, right heart pressures.
As a compensatory mechanism, pulmonary vasoconstriction occurs. The RV pressure increases resulting in RV hypertrophy
Elevated pulmonary pressure can progress to fixed pulmonary hypertension
Eventually, the RV fails…
Balloon Valvotomy
Procedure performed under local anaesthetic in Cardiac Catheterisation Lab
Inter-atrial septum puncture required
‘Inoue’ balloon inflated with guided fluoroscopy
Optimal result when both commissures are fused and non-calcified
Criteria for Valvotomy
Thickening largely confined to leaflet tips
Good mobility of anterior leaflet
Little chordal involvement
No more than mild MR
No left atrial thrombus present
No commissural calcification
Wilkin’s Score
The thickening, mobility, and calcification of the mitral leaflets as well as of the chordal involvement can be assessed and scored from 1 (mild) to 4 (severe).
The lowest score is 4, the highest is 16
A score <8 predicts feasibility and short and long term success of balloon valvuloplasty, defined as an increase in valve area of > 50%, valve area >1.5cm2, and < 2 + MR
Inoue Balloon
Calcified Postero-medial Commissure
Calcified Antero-lateral Commissure
Complications
Atrial Fibrillation
Heart failure
Blood clot in the left atrium (more likely if atrial fibrillation present)
Endocarditis (damaged valves are more prone to infection than normal valves)
Other Considerations
Severe aortic regurgitation (this can shorten mitral valve pressure half-time)
Right ventricular function
Intra-atrial thrombus
Reporting Mitral Stenosis
Appearance of valve
Severity of stenosis
Mitral regurgitation
Right-sided pressure and right ventricular function
Amenability to balloon valvuloplasty
Other valves
Role of exercise echocardiography
Baseline pictures acquired to assess severity
Peak exercise pictures acquired
Information:
Doppler assessment
Does PA pressure increase?